Technical Field
The present disclosure relates to a fixing device and an image forming apparatus using the fixing device.
Background Art
Recently, in order to reduce energy consumption and shorten wait time, that is, warming-up time, many new fixing devices used in image forming apparatuses such as printers, copiers, and fax machines have a so-called on-demand type structure that directly heats a small heat-capacity endless film-like belt.
Such new fixing devices using a quick-start-up (QSU) method include a rotatable endless free belt, a heater that is disposed inside a loop formed by the free belt and which directly heats the free belt, an elastic roller that contacts an outer surface of the free belt, and a pad that is disposed inside the loop formed by the free belt and extends in a longitudinal direction of the elastic roller. The pad, which is also called a nip formation pad and which elastically deforms the elastic roller, serves to broaden a contact region between a sheet of recording media and the free belt, that is, a nip width, if the belt is a relatively narrow one.
The free belt and the pad situated inside the loop formed by the free belt are set at a predetermined position with respect to the elastic roller, which is fixed on a shaft driven to rotate, to press the elastic roller and form a fixing nip while printing and, after printing, to move to a release position separate from the belt, in which the free belt does not press the elastic roller to avoid compression set of the elastic roller.
It is to be noted here that, conventionally, the heater and the pad are fixed together on a holder that is supported by a side plate and from which the free belt is suspended because the heater needs to be disposed at a predetermined constant clearance with respect to the free belt and the pad when the free belt and the pad press against the elastic roller and form the fixing nip.